@article {57918, title = {Automatic standardized processing and identification of tropical bat calls using deep learning approaches}, year = {2019}, abstract = {

Consistent and comparable metrics to automatically monitor biodiversity across the landscape remain a gold-standard for biodiversity research, yet such approaches have frequently been limited to a very small selection of species for which visual approaches (e.g., camera traps) make continuous monitoring possible. Acoustic-based methods have been widely applied in the monitoring of bats and some other taxa across extended spatial scales, but are have yet to be applied to diverse tropical communities.

In this study, we developed a software program \“Waveman\” and prepared a reference library using over 880 audio-files from 36 Asian bat species. The software incorporated a novel network \“BatNet\” and a re-checking strategy (ReChk) to maximize accuracy. In Waveman, BatNet outperforms three other published networks: CNNFULL, VggNet and ResNet_v2, with over 90\% overall accuracy and 0.94 AUC on the ROC plot. The classification accuracy rates for all 36 species are at least 86\% when analysed in combination. Moreover, our library preparation and ReChk greatly improved the sensitivity and reduced the false positive rate, when tested with 15 species for which more detailed and situationally diverse records were available. Finally, BatNet was successfully used to identify Hipposideros larvatus and Rhinolophus siamensis from three different environments. We hope this pipeline is useful tool to process bioacoustic data accurately, effectively and automatically, therefore allowing for greater standardization and comparability for researchers to understand bat activities across space and time and therefore provide a consistent tool for monitoring biodiversity for management and conservation.

}, keywords = {Algorithms, Automated monitoring, Automatic processing, bats, bioacoustics, Biodiversity metrics, Calls, Deep learning, echolocation, machine learning, Monitoring protocol, Neural network}, doi = {10.1016/j.biocon.2019.108269}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0006320719308961}, author = {Chen, Xing and Zhao, Jun and Chen, Yan-hua and Zhou, Wei and Hughes, Alice C.} } @article {57651, title = {Does bat response to traffic noise support the misleading cue hypothesis?Abstract}, year = {2019}, abstract = {

The world has become a noisier place due to the increase in urbanization. Noise is generally considered an impediment, altering an animal\’s behavior through masking or distraction. But noise can also provide useful information about the environment. For animals that rely on natural environmental noise as an indicator of favorable foraging conditions, increasing levels of anthropogenic noise might mislead informed decision-making. Bats use rain noise, a natural environmental cue, to delay their emergence from the roost, presumably to avoid sensory and metabolic costs associated with foraging in heavy rain. Here we tested the \“misleading cue hypothesis,\” asking whether traffic noise is mistaken for rain noise by bats. Given the acoustic similarity between rain noise and traffic noise, we predicted that bats would confuse the two. We conducted a playback experiment using rain, traffic, and ambient noise at natural roosts of common big-eared bats (Micronycteris microtis, Phyllostomidae) and recorded bat emergence behavior. In contrast to their response to rain noise, the bats did not delay roost emergence in response to traffic noise. Thus, we found that bats were able to discriminate between traffic noise and rain noise and were not misled by similarity in acoustic parameters in the two noise types, when emerging from their roost. Emerging bats did show more exploration flights during traffic noise than during rain noise, but not during ambient noise, suggesting that they perceive traffic noise as a novel acoustic cue. Our data provide new insights into perception of traffic noise by bats.

}, keywords = {anthropogenic noise, bats, evolutionary trap, Micronycteris microtis, misleading cues, Traffic noise}, doi = {10.1093/beheco/arz148}, url = {https://academic.oup.com/beheco/article/30/6/1775/5574811}, author = {Geipel, Inga and Amin, Bawan and Rachel A. Page and Halfwerk, Wouter}, editor = {Candolin, Ulrika} } @article {57607, title = {Sensory gaze stabilization in echolocating bats}, year = {2019}, abstract = {

Sensing from a moving platform is challenging for both man-made machines and animals. Animals\&$\#$39; heads jitter during movement, so if the sensors they carry are not stabilized, any spatial estimation might be biased. Flying animals, like bats, seriously suffer from this problem because flapping flight induces rapid changes in acceleration which moves the body up and down. For echolocating bats, the problem is crucial. Because they emit a sound to sense the world, an unstable head means sound energy pointed in the wrong direction. It is unknown how bats mitigate this problem. By tracking the head and body of flying fruit bats, we show that they stabilize their heads, accurately maintaining a fixed acoustic-gaze relative to a target. Bats can solve the stabilization task even in complete darkness using only echo-based information. Moreover, the bats point their echolocation beam below the target and not towards it, a strategy that should result in better estimations of target elevation.

}, keywords = {active sensing, bats, echolocation, gaze stabilization, sensory perception, tracking}, doi = {10.1098/rspb.2019.1496}, url = {https://royalsocietypublishing.org/doi/10.1098/rspb.2019.1496}, author = {Eitan, O. and Kosa, G. and Yovel, Y.} } @article {57576, title = {Vocal Development of Horsfield{\textquoteright}s Leaf-Nosed Bat Pups (Hipposideros larvatus)}, year = {2019}, abstract = {

Bats are an appealing animal for investigating the biological basis and evolution of speech-related traits in wild mammal systems. We investigated vocal development in Horsfield\&$\#$39;s leaf-nosed bat pups, Hipposideros larvatus. We found that newborn bats emit many types of isolation calls, including downward frequency modulation (DFM), arched frequency modulation (AFM), upward frequency modulation (UFM), and others. The gradual decrease of Euclidean distance measurements revealed that pup isolation calls (DFM, AFM, UFM) gradually change into adult social calls. Furthermore, one of the isolation call types (UFM type) encoded an individual signature. By contrast, we report that early echolocation calls and isolation calls develop in parallel. As pups develop, early echolocation calls gradually mature and transform into adult-like echolocation calls. The interval and duration of echolocation calls decreases, while the peak frequency and bandwidth of frequency modulation increases.

}, keywords = {bats, echolocation calls, individual signature, isolation calls, vocal development}, doi = {10.3161/15081109ACC2019.21.1.016}, author = {Chi, Tingting and LIU, Muxun and Tan, Xiao and Li, Yu and Xiao, Yanhong and Sun, Keping and Jin, Longru and Feng, Jiang} } @article {53540, title = {Noise as an informational cue for decision-making: the sound of rain delays bat emergence}, journal = {The Journal of Experimental Biology}, year = {2019}, month = {Sep-01-2020}, pages = {jeb.192005}, abstract = {

Background noise can have strong negative consequences on animals, reducing individual fitness by masking communication signals, impeding prey detection and increasing predation risk. While the negative impacts of noise across taxa have been well documented, the use of noise as an informational cue, providing animals with reliable information on environmental conditions has been less well studied. In the tropical rainforest, downpours can be intense and frequent. Strong rainfall may impede efficient orientation and foraging for bats that need echolocation to both navigate and detect prey, and can result in higher flight costs due to increased metabolic rates. Using playback experiments at natural roosts we tested whether two bat species, differing in their hunting strategies and foraging habitats, use rain noise as a cue to delay emergence from their roosts. We found that both species significantly delayed their emergence time during rain noise playbacks compared to silence and ambient noise controls. We conclude that bats can use background noise, here the acoustic component of rainfall, as a reliable informational cue to make informed decisions, here about whether to initiate foraging trips or remain in the shelter of their roosts. Our findings suggest that environmental background noise can sometimes be beneficial to animals, in particular in situations where other sensory cues may be absent.

}, keywords = {bats, decision-making, foraging, information cues, Noise, rain}, issn = {0022-0949}, doi = {10.1242/jeb.192005}, url = {http://jeb.biologists.org/lookup/doi/10.1242/jeb.192005https://syndication.highwire.org/content/doi/10.1242/jeb.192005https://syndication.highwire.org/content/doi/10.1242/jeb.192005}, author = {Geipel, Inga and Smeekes, Marcus J. and Halfwerk, Wouter and Rachel A. Page} } @article {53527, title = {Bats increase vocal amplitude and decrease vocal complexity to mitigate noise interference during social communication}, journal = {Animal Cognition}, year = {2019}, month = {Oct-01-2019}, abstract = {

Natural background noises are common in the acoustic environments in which most organisms have evolved. Therefore, the vocalization and sound perception systems of vocal animals are inherently equipped to overcome natural background noise. Human-generated noises, however, pose new challenges that can hamper audiovocal communication. The mechanisms animals use to cope with anthropogenic noise disturbances have been extensively explored in a variety of taxa. Bats emit echolocation pulses primarily to orient, locate and navigate, while social calls are used to communicate with conspecifics. Previous studies have shown that bats alter echolocation pulse parameters in response to background noise interference. In contrast to high-frequency echolocation pulses, relatively low-frequency components within bat social calls overlap broadly with ambient noise frequencies. However, how bats structure their social calls in the presence of anthropogenic noise is not known. Here, we hypothesized that bats leverage vocal plasticity to facilitate vocal exchanges within a noisy environment. To test this hypothesis, we subjected the Asian particolored bat, Vespertilio sinensis, to prerecorded traffic noise. We observed a significant decrease in vocal complexity (i.e., an increased frequency of monosyllabic calls) in response to traffic noise. However, an increase in the duration and frequency of social calls, as have been observed in other species, was not evident. This suggests that signal simplification may increase communication efficacy in noisy environments. Moreover, V. sinensis also increased call amplitude in response to increased traffic noise, consistent with the predictions of the Lombard effect.

}, keywords = {acoustic communication, bats, Noise, Social calls, vocal plasticity}, issn = {1435-9448}, doi = {10.1007/s10071-018-01235-0}, url = {http://link.springer.com/10.1007/s10071-018-01235-0}, author = {Jiang, Tinglei and Guo, Xiong and Lin, Aiqing and Wu, Hui and Sun, Congnan and Feng, Jiang and Kanwal, Jagmeet S.} }